King David vs. Jesus on the Topic of Enemies

Psalm 9

 ¹⁹ Arise, O LORD, let not man triumph;
       let the nations be judged in your presence.

 ²⁰ Strike them with terror, O LORD;
       let the nations know they are but men.

Psalm 52

¹ Why do you boast of evil, you mighty man?
       Why do you boast all day long,
       you who are a disgrace in the eyes of God?

 ² Your tongue plots destruction;
       it is like a sharpened razor,
       you who practice deceit.

 ³ You love evil rather than good,
       falsehood rather than speaking the truth.
       Selah

 ⁴ You love every harmful word,
       O you deceitful tongue!

 ⁵ Surely God will bring you down to everlasting ruin:
       He will snatch you up and tear you from your tent;
       he will uproot you from the land of the living.
       Selah

Various psalms contain appeals to God to pour out His wrath upon the psalmist's enemies. These seem to contradict the Christian stance of love towards one's enemies. Nevertheless, it is a mistake to explain away these expressions as degenerate and sub-Christian sentiments which have been permitted in the sacred canon by the principle of "progressive revelations."  Progressive revelation is not to be thought of as a progress from error to truth, but rather as a progress from the partial and obscure to the complete and clear.  A consistent Evangelical must hold that all portions of the Word of God are true in the sense intended by the original author under the inspiration of the Holy Spirit, even though couched in terms which may perhaps have been more comprehensible and relevant to God's people at the time of composition than in later ages.

This last line explains to me why certain Old Testament practices which a 21st century reader would find backward at the least were not out-and-out condemned as I believe they were more cultural than mandated or approved by God.  This also states why certain things that were understandable or normal back then don't have to carried on today.  I think we can move past some of the ancient mindsets such as slavery being permitted, women being property and polygyny a cultural norm.  Cultures do evolve over time. Technology changes.  It's not innovation to live in the century in which you were born.  The Taliban doesn't have to ban toothpaste so everyone can use the miswak as the Islamic prophet did.

It is important to realize that prior to the first advent of Christ, the only tangible way in which the truth of the Scripture could be demonstrated to human observers was by the pragmatic test of disaster befalling those who were in error and deliverance being granted to those who held to the truth.  As long as the wicked continued to triumph, their prosperity seemed to refute the holiness and sovereignty of the God of Israel.  A Hebrew believer in the Old Testament age could only chafe in deep affliction of soul as long as such a state of affairs continued. 

Do you ever think the same way when you see evil people triumphing while seemingly good people are suffering?

Identifying himself completely with God's cause, he could only regard God's enemies as his own, and implore God to uphold His own honor and justify His own righteousness by inflicting a crushing destruction upon those who either in theory or in practice denied His sovereignty and His law.  Not until the supreme exhibition of God's displeasure at sin, demonstrated by the death of His Son upon the cross, was it possible for the believer to wait patiently while God's longsuffering permitted the wicked to enjoy his temporary success. Nor was the longsuffering of God properly understood until Jesus came to earth to teach His love to men.

Here is a bit of Jesus' teachings as recorded in the fifth chapter of Matthew.

You have heard that it was said, 'Love your neighbor and hate your enemy.' But I tell you: Love your enemies and pray for those who persecute you, that you may be sons of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. If you love those who love you, what reward will you get? Are not even the tax collectors doing that? And if you greet only your brothers, what are you doing more than others? Do not even pagans do that? Be perfect, therefore, as your heavenly Father is perfect.

Do we tend to revert back to centuries past in how we deal with enemies, live our lives today, justify what we do? Or do you think we have successfully "evolved" into better people?  Why do you think the way that you do?  What do you think about what Archer said regarding progressive revelation?  Did his commentary on this matter make sense?  Had you also noticed and been bothered at David's attitude towards his enemies when comparing them to Jesus' teaching about loving our enemies? How had you reconciled the two?

except for Bible verses, all quotes in blue are from pg. 452-453 
A Survey of Old Testament Introduction by Gleason L. Archer, Jr.